1 - Are there alot of scammers around in the marketplace?
Yes. Not a TON, but there are enough that you have to watch out.
2 - Where are vouches being saved/stored because I see no vouch system nor a reputation system.
This isn't a vouching or reputation system. This forum is for all aspects of bitcoins, including development and technical support and discussion about mining etc etc etc. The marketplace is just a small subset of everything that goes on here, so it's not really designed to have a reputation system (although that would be nice). Best thing is just to look at the history of a user you're considering transacting with, whether they've had any other successful transactions with users here, how old their account is, etc.
3 - What are people interested in on these forums these days?
You name it. Lots of people have bitcoins looking for a home. And lots of people have stuff looking to get bitcoins. Browse around the marketplace forums and see for yourself what all the possibilities are. I haven't seen too many "requests" for things, except certain steam games, but there are many people selling steam games here so it's pretty competitive from that standpoint anyway.